Design And Construction Of A Remote Controlled Tri–band Frequency Jammer.

The operation of power supply is as shown:
The transformer which transforms 220V AC to other levels of voltages. Its functions are outlined below:
i.    Rectification: Convert the AC voltage to DC voltage.
ii.    Filtering: “Eliminate the noise” so that a constant DC voltage is produced. This filter is just alarge capacitor used to minimize the ripple in the output.
iii.    Voltage Regulation: It provides the desired DC voltage.
The step down transformer steps down the input voltage from 220V AC to 12 V AC. This is then converted to a DC voltage by the diode bridge rectifier. Rectification is the conversion of alternating current to direct current. In this process the diode(s) allows current to flow in only one direction. A full-wave rectifier which is used in this case converts the whole of the input waveform to one of constant polarity (positive or negative) at its output. Here, four diodes in a bridge configuration is employed.
Direct current that has only been rectified, however, has various changes in voltage (ripples) lingering from the alternating current. The capacitor filters out these ripples to produce a more stable direct current supply.
For the signal jammer, the voltage required is +5V DC. So, the filtered 12V DC which comes out of the capacitor is regulated to 5V DC by a voltage regulator (7805) which is required for the main circuit. A voltage regulator functions by comparing its output voltage to a fixed reference and minimizing this difference with a negative feedback loop. Another capacitor is employed to further filter the voltage.
3.3.2    Remote control section
When a TV or DVD remote transmitter (shown in the figure below) is faced towards the TSOP1738 and any key is pressed on it. The TSOP 1738 module receives the train of 38 KHz IR pulses from the remote that makes its output to oscillate too. These pulses are inverted at the collector of T1, which finally go to the clock input of the decade counter. The arriving pulses could increment the CD4017 counter at the same rate (38 kHz), but because of the presence of the RC filter circuit (R1 = 100 k, C1 = 10 uF) between the collector and the ground, the train of pulses appear as a single pulse to the counter. Thus, on each key pressing, the CD4017 counter advances only by a single count. When the user releases the key, the C1 capacitor discharges through the R1 resistor, and the clock line is back to zero. So every time the user presses and releases a key on the remote, the CD4017 counter receives a single pulse at its clock input.

Car Audio Remote Controller was used as a transmitter instead of build a similar transmitter because it is cheap and portable.